Method of printing an embossed pattern along the peripheral band of a toroidal article



July 29, 1969 A. PACCIARINI ETAL 3,458,612

METHOD OF PRINTING AN EMBOSSED PATTERN ALONG THE PERIPHERAL BAND OF A TOROIDAL ARTICLE Original Filed March 3. 1965' ll Sheets-Sheet 1 3 INVENTORB:

22 WI, Amwzw Pzccmrwzo & Dara'o 6. 55165% ATTORNEYS July 29, 1969 A. PACCIARINI ETAL 3,458,612

METHOD OF PRINTING AN EMBOSSED PATTERNALONG THE A PERIPHERAL BAND OF A 'rononm, ARTICLE original Filed March a, 1965- 11 Sheets-Sheet 2 m m m m WW2 11 020 wk 0 ,w m :00 n 4 {a J,

Wmpm w fiwh ATTORNEY 8 VA. PACCIARINI ETAL July 29, 1969 3,458,612 METHOD OF PRINTING AN EMBOSSED PATTERN ALONG THE PERIPHERAL BAND OF A TOROIDAL ARTICLE Original Filed March 3, 1965 ll Sheets-Sheet 5 lllll INVENTQRS Amfmw Paccc'ara'm & Dania 'b'kiia,

July 29, 1969 A. PACCIARINI ETAL 3 45 512 METHOD OF PRINTING AN EMBOSSED PATTERN ALONG THE PERIPHERAL BAND OF A TOEOIDAL ARTICLE Original Filed March 3. 1965 11 Sheets-Sheet 4 INVENTCRs Antonio Pacczlara'ni 51 Dario lfla A RNEY8 July 29, 1969 PACCIARINI ETAL 3,458,612 METHOD OF PRINTING AN EMBOSSED PATTERN .ALONG THE PERIPHERAL BAND OF A TOROIDAL ARTICLE Original Filed March 3. 1965 ll Sheets-Sheet 5 .INVENTORS July 29, 1969 A. PACCIARINI ETAL 3,458,612

METHOD OF PRINTING AN EMBOSSED PATTERN ALONG THE PERIPHERAL BAND OF A TOROIDAL ARTICLE 11 Sheets-Sheet 6 Original Filed March 3, 1965 m 0 mm wr mam g 6 d PG w w P o &

ir/mam M M TITORNEYS July 29, 1969 A. PACCIARINI ETAL 3,458,612

METHOD OF PRINTING AN EMBOSSED PATTERN ALONG THE PERIPHERAL BAND OF A TOROIDAL ARTICLE Original Filed March 3, 1965 I l1.Sheets-Sheet 7 92 93 9g INVENTOIZS Antonia Pacciarmz & Dam/a 62mm ATTORNEYS A PACCIARINI ETAL I 3,458,612 METHOD OF PRINTING AN EMBOSSED PATTERN ALONG THE July 29, 1969 PERIPHERAL BAND OF A TOROIDAL ARTICLE 11 Sheets-Sheet 8 Original Filed March 3, 1965 7 n S a m N. ,6 m m m 0 w M mu ,6 ,0 ,w la n m wD n X & Z O m an 3 a BYS ATTORNEU y 29, 1959 A. PACCIARINI ETAL 3,458,612

METHOD OF PRINTING AN EMBOSSED PATTERN ALONG THE PERIPHERAL BAND OF A TOROIDAL ARTICLE 11 Sheets-Sheet 9 Original Filed March 5, 1965 MNN HVVENTORJ ORNEYS l m v8 4 in m r, a w m 7 a N W P .m. w NR. m 0 1 QM m m T A 0 8w 9w mow WNN a kQN m Qx x Qw QM kw y 1969 A. PACCIARINI ETAL 3,458,612

METHOD OF PRINTING AN EMBOSSED PATTERN ALONG THE PERIPHERAL BAND OF A TOROIDAL ARTICLE Original Filed March 3. 1965 ll Sheets-Sheet 10 mvmons Anton/o Pace/brim Dar/o Gila/la ATTORNEYS J l 29 19 9 A. PACCIARINI ETAL 3,458,612

METHOD OF PRINTING AN EMBOSSED PATTERN ALONG THE PERIPHERAL BAND OF A-TOROIDAL ARTICLE Original Filed March 3, 1965 11 Sheets-Sheet 11 INVENTORS Anton/o Pacciar/h/ Oar/'0 Gila/ta A ORNEYS United States Patent 3,458,612 METHOD OF PRINTING AN EMBOSSED PATTERN ALONG THE PERIPHERAL BAND OF A TOROI- DAL ARTICLE Antonio Pacciarini and Dario Giletta, Milan, Italy, assignors to Pirelli Societa per Azioni, Milan, Italy Application Mar. 3, 1965, Ser. No. 438,825, now Patent No. 3,337,918, dated Aug. 29, 1967, which is a continuation-in-part of application Ser. No. 342,865, Feb. 4, 1964, which in turn, is a continuation-in-part of applications Ser. No. 206,088, and Ser. No. 206,089, June 28, 1962. Divided and this application Jan. 5, 1967, Ser. No. 632,839

Claims priority, application Italy, July 7, 1961, 12,473/61; Patent 658,679; Feb. 10, 1962, 2,639/ 62, Patent 665,377; Aug. 4, 1964, 17,022/ 64, Patent 797,871

Int. Cl. B2911 5/02 US. Cl. 264-94 19 Claims ABSTRACT OF THE DISCLOSURE A method of forming an embossed pattern upon the peripheral surface of an article of toroidal cross section comprising the steps of first enclosing all the exterior surfaces of said article except the peripheral surface thereof within rigid surfaces, and subsequently bringing at least one additional rigid surface into contact with said peripheral surface in order to enclose said article completely. The additional rigid surface has a plurality of projections extending therefrom which produce cavities in the peripheral surface thereof in accordance with the embossed pattern This application is a division of application Ser. No. 438,825 filed Mar. 3, 1965, now Patent No. 3,337,918 which is a continuation-in-part of an earlier application of the applicants, Ser. No. 342,865 filed Feb. 4,1964, wh ch, in turn, is a continuation in part of applicants applications Ser. No. 206,088 and Ser. No. 206,089, each filed June 28, 1962 and each of the last three mentioned appllcations are now abandoned.

The present invention relates to a method for printing an embossed pattern along the peripheral band, in the plastic state, of a toroidal article and, in particular, on the tread band of a pneumatic tire provided with a ringshaped reinforcing structure placed between the carcass and the tread, the function of the structure being to stiffen the tread hand both in longithiudinal and transverse direction. The ring-shaped reinforcing structure has a width substantially equal to that of the tread band and must possess a high resistance to tension, in order to withstand the longitudinal stresses due to the inflation pressure, together with a highly reduced or substantially negligible extensibility. Also the structure must be completely symmetrical relative to the beads of the tire due to the fact that in actual use on a vehicle the tire tends to displace the wheel upon which it is mounted in a direction normal to the direction of rotation with a force that is considerable even for a few millimeters of asymmetry of the reinforcing structures.

In order to obtain a pneumatic tire provided with a ring-shaped reinforcing structure having the above described features, great accuracy is required in all the operations for the construction of the tire and in particular during the molding and the vulcanization by means of which the various elements of the tire are settled and assembled in final form. In the past, the molding and vulcanization of such tires were carried out, in conventional vulcanizing units, within two half-molds mating with each other along a plane passing through the mid-circumfer- Patented July 29., 1 969 ential line of the tire, the inner peripheral surfaces of said half-molds being provided with blocks and with undulated laminae radially projecting and corresponding to the cavities to be formed in the tread band. However, the tire, to be introduced into the mold, had to have an outer diameter less than the diameter corresponding to said inner projections and therefore it was necessary to increase the diameter thereafter so that the projections would penetrate the tread band being embossed.

In the same process, the tire was at first introduced into the lower half-mold, still hot due to the treatment of the previously cured tire, and its sidewall, upon coming in contact with said half-mold, assumed the shape of the profile of the latter by reason of the tires own weight and temperature of the mold, whereas one-half of the tread band penetrated partially between the projections existing inside the peripheral band. Then, the upper half-mold was brought into contact with the lower half-mold and then compressed fluid was injected into the tire, either directly in contact with its inner surface, or into a curing bag previously provided in the tire itself.

In the above process, it often happened that the upper half-mold, during its lowering, exerted a prejudicial tangential action on the free half of the tread band and that the subsequent injection of compressed fluid did not result in a symmetrical settling of the tire with respect to its mid-circumferential plane, since the lower half of the tire was not free to move like the upper one, it being already partially connected with the tread in the projections of the lower half-mold. Moreover, the fact that the tire had to be increased in diameter so that its peripheral band could penetrate completely between the projections, involved an elongation and/ or an angular displacement of the reinforcing cords of the ring-shaped reinforcing structure which is incompatible with the desired inextensibility or very reduced extensibility of the same.

All the above cited factors had a negative influence on the regularity of the tire, causing irregular yieldings and truing up defects in both the reinforcing structure and in the tread.

In an attempt to eliminate the above described problems, it was proposed to use a mold having an upper section and a lower section in the form of a continuous ring, and a series of sectors corresponding to the desired tread band. However, the centripetal displacement of the sectors took place immediately after the tire was introduced into the lower half-mold due to the movement of the upper section toward the lower section. While this avoided the problems of the former method described above with respect to elongation or angular displacements of the cords of the reinforcing structure, because it was no longer necessary to increase the diameter of the tire, the problem of faulty settling of the tire in the mold was not thereby solved.

An object of the present invention is a novel method for printing an embossed pattern along the peripheral band, in the plastic state, of a toroidal article which consists in confining said article with rigid surfaces whose profile corresponds to the final profile of the article, without engaging the peripheral band, and in subsequently compressing said peripheral band radially inwardly by simultaneously bringing a plurality of rigid surfaces provided with radial projections corresponding to the cavities or recesses to be formed in the band into contact with the band until the article is outwardly completely delimited by said rigid surfaces. During the compression of the peripheral band of the article radially inwardly, the centripetal displacement of the inner surface of the article, if it is hollow, is prevented either by providing inside it a solid core, or a core inflatable at a pressure higher than the pressure exerted from outwardly against the peripheral band, or else by injecting compressed fluid in direct contact with said inner surface, at a pressure higher than that exerted from outwardly.

In order to cure the molded article, the mold is surrounded with a heated fluid subjected to a pressure higher than the above pressure. Moreover, in the case of a hollow article, heated compressed fluid is directly injected inside the article itself or inside the inflatable core contained therein.

These and further features of the invention will appear more clearly from the following description, made with reference to the attached drawings, in which:

FIG. 1 is a vertical section of a curing unit for pneumatic tires into which a curing bag has been previously introduced separately, said curing unit comprising an apparatus for carrying out the method of the present invention;

FIG. 2 is a side elevational view of the unit shown in FIG. 1, with portions thereof broken away for illustration purposes;

FIG. 3 is a horizontal section on line 33 of FIG. 1;

FIG. 4 is a fragmentary detailed section of the curing unit as in FIG. 1, on an enlarged scale, and with the central mold section in open position;

FIG. 5 is a fragmentary detailed section of a curing unit having a curing bag and provided with another form of apparatus for carrying out the method of the present invention;

FIG. 6 is a fragmentary section like FIG. 5, but still another embodiment of apparatus for carrying out the method of the present invention;

FIG. 7 is a transverse vertical section, with parts shown in elevation, of a vulcanizing or curing unit for pneumatic tires provided with an incorporated curing bag;

FIG. 8 is a side elevational view of the apparatus of FIG. 7, in its open position, and with some parts being shown in section;

FIG. 9 is a fragmentary detailed section of a curing unit having a curing bag and provided with a further form of apparatus;

FIG. 10 is a section of FIG. 9, taken along plane 10- 10, and

FIG. 11 is a fragmentary detailed section of still another curing unit having a curing bag.

The curing unit represented in FIGS. 1, 2, 3 and 4 comprises a frame 1 bearing a cylindrical container 2 whose bottom is provided with a central hole 2a passed through downwardly by a single-acting cylinder 3, provided with an opening 4 for the injection and the discharge of a compressed fluid. Inside the cylinder 3 there is slidably mounted a piston 5 whose stem 6, in correspondence of its upper end, supports a circular plate 7 onto which there are assembled the lower section 8 and the central section 9 of a mold. The lower section 8 has an annular continuous shape, whereas the central section is subdivided into a plurality of sections, provided on their inner surface with projections corresponding to the cavities or recesses which are to be obtained on the tread band to be embossed. The sectors 9 are assembled on supports 10, each sector being provided with two lateral guides 11 and with an inclined plane 12 in the form of a plate mounted between the guides 11.

In contact with the plate 12 and inserted between each pair of guides 11, there is a second inclined plane 13, in the form of a plate integral with the frame 1 by means of the supporting ring 14. The upper section 15 of the mold has an annular continuous shape and is supported by the plate -16 assembled inside the cover 17 of the container 2. The cover 17 is secured to the lower part of a transverse beam 18 provided at both ends with a pivot 19 supported in the upper end of a lever 20, which is pivoted at the opposite end about a pivot pin 21 fixed on and carried by a sprocket wheel 22 assembled upon the supports 23 and 24 of the frame 1.

At both sides of the curing unit there is a plate 25, integral with the frame 1 and provided with a vertically extending guide surface 26 and with an inclined guide surface 27, along which can slide a roller 28 rotatably assembled on the pivot 19.

The plates 25 are each provided with a second vertical guide slot 29 into which can slide a second roller 30 fixed on and carried by vertical arms 29 mounted on and depending from opposite sides of beam 18.

The sprocket wheel 22 is actuated in both rotative directions through the gear 31 which meshes with the pinion 32 keyed on the shaft 33; on the midline of the latter there is assembled the gear 34, actuated by the reversing motor 35 through the endless screw 36.

In order to mold the tread band of a tire 37, at least partially shaped, into which the curing bag 38 has already been introduced, compressed fluid is at first injected through the opening 4 of the cylinder 3 to raise the piston 5 as far as the upper end of said cylinder and to lift at the same time the plate 7 supporting the lower section 8 and the central section 9 of the mold, so that the sectors 9 may be radially outwardly displaced from the lower section 8 of the mold. Then the tire 37 is disposed on the lower section 8 of the mold and the sprocket wheels 22, through the endless screw 36 and the gears 34, 32 and 31, are actuated by the motor 35 in order to bring the pivots 21 from the upper position they have in FIGURE 2 to the nearest position shown in FIGURE 1 to the base of the frame 1.

As a result of the rotation of the wheels 22, the crank mechanism, constituted by the levers 20 and by the beam 18, rotates the cover 17 about the pivots 19 until the assemblage reaches a horizontal position, and this movement is controlled by means of the rollers 28 which ascend by rolling along the guides 27. The cover 17, still in consequence of the rotation of the wheels 22, is therefore lowered, remaining always parallel to itself. This vertical movement is controlled by means of the rollers 28, which are now descending into the vertical guides 26, and by means of the rollers 30 which are also descending into the vertical guides 29. The upper section 15 of the mold, during its downward movement together with the cover 17, engages on the upper head of the tire and pushes it downwardly to a position in contact with the lower section 8 of the mold. At this moment compressed fluid is injected into the curing bag. The plate 16, continuing to move downwardly, pushes in the same direction the plate 7 and the elements supported by it, with a pressure which is higher than the pressure of the fluid existing below the piston 5, whereby the fluid is caused to return to the feeding source through the opening 4 of the cylinder 3. The lowering of the plate 7 actuates the sliding of the inclined plates 12 along the stationary inclined plates 13 and the consequent inward radial displacement of the sectors 9 which, by means of the projections provided on their inner surface, penetrate the tread band. At this moment the cover 17 comes into contact with the upper edge of the circular wall of the container 2, isolating the mold from the outer room, and therefore the curing of the tire can be carried out in the conventional way by injecting additional compressed fluid into the curing bag 38 in order to increase the pressure therein and by injecting pressurized steam into the container 2.

To remove the cured tire from the mold, after the rclease of the steam from the container 2 and of the compressed fluid from the bag 38, the above described move ments are carried out by following an inverted sequence.

In the embodiment illustrated by FIGURE 5, the lower section 40 and the central section 41 of a mold are assembled on a circular plate 39. The lower section 40 has an annular continuous shape, whereas the central section 41 is subdivided into a plurality of sectors each provided on its inner surface with projections corresponding to the cavities or recesses to be obtained on the tread band to be molded. The sectors 41 are assembled on supports 42, each provided with lateral guides 43 and having an inclined plane or plate 44 disposed between guides 43. In

contact with the inclined plane 44 and inserted between each pair of guides 43, there is a second inclined plane or plate 45, integral with the frame base of the curing unit through the supporting ring 46. The upper section 47 of the mold is supported by the plate 48 assembled inside the cover 49 of the container 56. In the central part of the plate 48 there is a slidably mounted stem 51, whose lower end has a semi-spherical shape. The stem 51 is actuated by a piston not shown in the figure.

In the central part of the circular plate 39 there is assembled a cylinder 52 extending downwardly, which is provided on its bottom with an opening for the injection of the curing fluid. Between the lower section of the mold and the cylinder 52 there are clamped the thickened edges 53 of a flexible curing bag 54. The plate 39 and the elements supported by it can be pushed upwardly by a piston also not shown in the figure.

In order to emboss the tread band of a tire 55 at least already partially shaped, the plate 39 is at first raised to bring it to the position represented in the figure in order that the sectors 41 may be outwardly radially displaced from the lower section 40 of the mold. Then the tire 55 is disposed on the lower section 40 of the mold and the plate 48 and the cover 49 are rotated and lowered, as described in connection with the embodiment illustrated in FIGS. 1-4. Then the stem 51 is pushed downwardly and, when the upper section 47 of the mold, during its lowering, engages with the upper bead of the tire, compressed fluid is injected through the opening provided on the bottom of the cylinder 52; in this way the compressed fluid pushes upwardly the curing bag 54 contained in the cylinder 52 and causes the central part of said curing bag to engage with the lower end of the stem 51. While the upper section 47 of the mold approaches the lower section 40, the stem 51 is progressively withdrawn towards the top so that the curing bag 54 may gradually mate with the inner surface of the tire 55 starting from its clamped edge. The stem 51, therefore, acts to delay the displacement of the central portion of bag 54 relative to its side portions, the result being that the bag expansion into the tire occurs uniformly or evenly about the tire axis. When the lower surface of the plate 48 comes into contact with the upper surface of the sectors 41 and of their supports 42, the beads of the tire are at a definitive mutual distance and the tire is in contact with the inner surface of the sections 40 and 47 of the mold.

The plate 48, in its further downward movement, pushes downwardly the plate 39 and the elements supported by it with a pressure higher than the pressure exerted by the fluids existing below the piston, which had raised the plate, so that said fluid is forced to return to its feeding pipe. The lowering of the plate 39 causes the sliding of the inclined planes or plates 44 along the stationary inclined planes or plates 45, thus actuating the radial approaching of the sectors 41, which cause their projections to penetrate the surface of the tread band and close the mold completely. At this moment also the cover 49 comes into contact with the upper edge of the container 50, isolating the mold from the outer room. Then the curing of the tire is carried out in the conventional way by injecting additional compressed fluid into the curing bag 54 in order to increase the pressure therein, and by injecting pressurized steam into the container 50.

After curing, the tire is removed from the mold by repeating the above described operations with an inverted sequence, and the curing bag 54 is removed from the inside of the tire 55 by pushing it into the cylinder 52 by means of the stem 51.

In the embodiment depicted by FIGURE 6-, the lower section 57 and the central section 58 of a mold are assembled on a circular plate 56. The lower section 57 has an annular continuous shape, whereas the section 58 is constituted of a plurality of sectors each provided with radial projections on its inner surface. The sectors 58 are assembled on supports 59, each provided with lateral guides 60 and having an inclined plane or plate 61 comprised between said guides 60. In contact with the inclined plane 61 and inserted between each pair of guides 60, there is a second inclined plane or plate 62, integral with the frame base of the curing unit through the supporting ring 63. The plate 56 is assembled on the upper end of a hollow stem 64 passed through by a second slidably mounted stem '65 carrying on its upper end a disc 66. A curing bag 67 is clamped at its thickened upper edges between the disc 66 and a ring 68 and at its lower edges between a plate 69, fixed on and carried by a plate 56, and a disc 70.

FIGURE 6 shows, moreover, a cylindrical container 71 which is in the indicated position only during the insertion of the curing bag 67 into the tire 72.

In order to emboss the tread band of a tire 72 at least partially shaped, the plate 56 is brought to its upper position, shown in FIGURE 6, so that the central sectors 58 of the mold assume positions spaced radially outward from the lower section 57, and the disc 66 is pushed upwardly until the curing bag 67 assumes a cylindrical shape. Then the tire 72 is telescopically threaded about the curing bag 67 until its lower bead engages with the lower section 57 of the mold. Subsequently the cylindrical container 71 is also telescopically threaded about the bag 67 and is pushed downwardly until its lower edge engages with the upper bead of the tire. Then the disc 66 is progressively lowered and at the same time, through an opening, not indicated in the figure, compressed fluid is injected into the bag 67 which, sliding along the inner surface of the container 71, gradually expands into the tire 72 and mates with its inner surface. When the bag 67 has completely penetrated inside the tire 72, the container 71 is removed and the cover of the curing unit is rotated and lowered, as already described in respect of the curing unit represented in FIGS. 1-4.

While the cover of the curing unit moves toward the closed position, the upper half mold, which is fast with it, engages with the upper bead of the tire and pushes it downwardly until it has reached the definitive distance from the other head. At this moment additional compressed fluid is injected into the curing bag 67 to oppose the pressure which is exerted immediately afterwards on the tread band by the sectors 58 in consequence of the sliding of the inclined planes or plates 61 along the inclined planes or plates 62 by virtue of the lowering of the plate 56, pushed downwardly by the upper portion of the curing unit.

When the mold is completely closed, additional compressed fluid is injected into the curing bag 67 to increase the pressure therein and the curing operation is carried out as described above.

For the removal of the cured tire from the mold, the above indicated operations are repeated in an inverted sequence; in this second phase, however, the presence of the container 71 is not necessary.

It is understood that the details of the apparatus which control the radial displacement of the central sectors of the mold in the method of the present invention can be varied without departing from the spirit and the scope of the present invention. Likewise, it is not indispensable to provide an inflatable core inside the article to be molded because, while in the case of normal tires this core is preferred, in the case of tubeless tires, which are practically impermeable, said core is not required. Also in the case of articles of another kind, the use of a solid or rigid core can prove more advantageous.

In addition, the curing operation may involve only the surface on which the embossed pattern is to be molded, as for instance in the retreading of worn out tires with a new tread band.

The method forming the object of the present invention has remarkable advantages in respect to those heretofore practiced. In fact, by enclosing the article for the first time between two parallel sections of the mold, which do not impinge upon the peripheral band to be molded, this band remains prefectly trued up, as it is relatively completely free up to the position of the complete closure of the mold which is carried out by radial compression, so that any tangential stress on said band is completely avoided. When compressed fluid is injected into the tire, it is free to symmetrically settle with respect to its midcircumferential plane. Moreover, the fact that it is no longer necessary to increase the outer diameter of the tire, prevents any irregular yielding due to the elongation of the cords and permits, in the case of tires provided with ring-shaped reinforcing structures, said structures to be built with a diameter practically equal to the final one.

The embodiment as shown in FIGS. 7 and 8 was evolved and produced because of certain difiiculties that occurred in the utilization of the embodiment as shown by FIG. 5. These difiiculties occurred in printing a pattern on the tread band of relatively large pneumatic tires having been of the type heretofore described. Such difficulties were found virtually nonexistent in smaller tires. However, with larger tires of increased weight it was found:

(a) Virtually impossible to include in the apparatus means for automatically detaching the treated tire from the lower section of the mold due to the presence of the cylindrical housing for the diaphragm in the central lower part of the device and of the stem for operating the diaphragm in the central upper part of the same, this deficiency being particularly notable whereupon the tires were subjected to the heat treatment when they tended to adhere to the mold as a result thereof.

(b) Very diflicult with a flexible diaphragm of a cylindrical shape to insert the diaphragm in the hollow toroidal article in such a way that it may uniformly mate with the inner surface of the same, due to the cylindrical shape of the diaphragm because folds take place, therefore an evenly distributed pressure is not exerted on the inner surface of the toroidal body and localized protuberances often are caused in the article. If the article, as in the case of a pneumatic tire, is subjected to a subsequent heat treatment and the diaphragm is made of rubber, both the protuberances of the article and the folds of the diaphragm become permanent and the tire must be rejected as unserviceable.

(c) The disposition of the housing for the diaphragm in the lower part of the apparatus caused difliculties. In fact, when the diaphragm was returned to its housing after the treatment of the article, it would again take the shape of a cylinder open at the top so that the condensate formed on the face of the diaphragm opposite to that which contacts the compressed fluid collects on the bottom of the cylindrical diaphragm, and when the latter is again inserted into another tire to be treated, the condensate penetrates between the inner surface of the article and the diaphragm and gives rise to considerable difficulties.

It is therefore a further object of the present invention to provide a method for automatically removing the flexible curing bag from the inside of the treated hollow body without resorting to mechanical means, which consists in creating a positive difference of pressure between the outer surface and the inner surface of the flexible curing bag in order to cause the ejection of the same from the inside of the hollow article.

The vulcanizing or curing unit represented in FIGS. 7 and 8 is constituted by a frame 81 onto which is assembled a cylindrical container 82 provided on its back with an opening 83 for the injection and the release of the compressed vulcanizing fluid, and on its bottom with a central hole, passed through downwardly by a doubleacting cylinder 84 provided with an opening 85 for the injection and the release of the compressed fluid below the piston 86 and with an opening 87 connected to a tube 88. The tube is integral with the cylinder 84 and is disposed inside the hollow stem 89, which is provided in its lower portion with an opening 90 for the injection and the release of compressed fluid from the chamber of annular section disposed over the piston 86.

The stem 89, in correspondence to its upper end, supports a circular plate 91 whose edge is so shaped as to receive the head of a pneumatic tire. On the bottom of the cylinder 84 there are slidably mounted two sliding blocks 92 passed through by a pivot 92 onto which is pivoted the end of a lever 93. The opposite end of said lever is keyed on a shaft 94 rotatably assembled in the frame 1. At the two sides of the lever 93, in a position symmetrical to it, two cylinders 95 and 96 are assembled on the frame 81. Within said cylinders slide two pistons, whose stems 97 and 98 are each pivoted at one end of the corresponding levers 99, whereas the opposite ends of levers 99 are keyed on the shaft 94. In the central part of said shaft there is keyed a lever 100, whose other end, shaped as a fork, is engaged into a block 101 which, when the vulcanizing unit is closed, is in contact with the stem 102, connected to the piston slidable into the single-acting cylinder 103 provided with an opening 104 for the injection and the release of a compressed fluid. Fixed on the upper end of the cylinder 84, there is assembled an annular plate 105 onto which lie the lower section 106 and the intermediate section 107 of a mold. The lower section 106 has a continuous annular shape, whereas the intermediate section 107 is divided into a plurality of sectors, provided on their respective inner surfaces with projections corresponding to the recesses which are to be obtained on the band to be molded. The sectors 107 are assembled on supports 108, each provided with two lateral guides, and having an inclined plane or plate 109 disposed between said guides. A second inclined plane or plate 110, integral with the frame 81 by means of the supporting ring 111 and disposed between each pair of said guides, is provided in contact with the plate 109. The upper section 112 of the mold has a continuous annular shape and is supported by the plate 113 assembled inside the cover 114 of the container 82. The cover 114 is secured to the lower part of a transverse beam 115 provided at both ends with a pivot 116, supported at the upper end of a lever 117 pivoted at the opposite end in a pivot 118 secured on a sprocket wheel 119 assembled in the supports 120 and 121 of the frame 81. At the two sides of the beam 115 there are fastened the plates 122 and 123, wherein the opposed pairs of rollers 124 and 125 are slidably mounted. At the two sides of the frame 81 there are assembled, integral with it, the two plates 126 and 127 each provided with a vertical guide 128 and with an inclined guide 129 along which can slide the rollers 124, and with a further vertical guide 130 along which can slide the rollers 125.

The pair of sprocket wheels 119 are actuated in both directions through the gears 131, which mesh with the pinions 132, keyed on the shaft 133 of the reduction gear 134, by means of the reversible motor 135.

The top of the beam 115 carries an endless screw 116 which meshes with a helical gear 137, assembled in a housing 138 and provided with an axial threaded hole into which is engaged a screw 139. At the lower end of said screw 139 is secured a cylinder 140 opening downwardly and provided at the opposite side with a hole 141 for the injection and the release of the compressed fluid used for molding and vulcanizing the pneumatic tire 142 enclosed in the mold and for eliminating the condensate formed within the cylinder 140. Between the lower edge of the cylinder and the upper section 112 of the mold there is clamped the thickened edge 1-43 of a curing bag 144 of toroidal shape, corresponding to the shape of the tire which it is wished to obtain. The curing bag 144 is encased in the cylinder 140 when the vulcanizing unit is not operative.

In order to mold and vulcanize a penumatic tire 142, at least partially shaped, the vulcanizing unit being closed as shown in FIG. 7, the cover 114 is raised and the motor is actuated. Said motor, through the reduction gear 9 134 and the gears 132 and 131, rotates the sprocket wheels 119 in such a way that the pivots 118 are brought to the position corresponding to the top dead center.

With further respect to the rotation of the wheels 119, the crank gear constituted by the levers 117 and by the beam 115 first raises the cover 114, maintaining it parallel to itself, and then causes it to rotate about the pivots 116 to an angle slightly greater than 90. These movements are guided by means of the rollers 124 and 125 which slide in the guides 128, 129 and 130.

Simultaneously with the lifting of the cover 114, compressed fiuid is progressively injected through the opening 104 of the cylinder 103, in order that the stem 102 may impart a small rotation to the lever 100 by means of the block 101 in contact with the same. This small rotation causes a reduced lifting of the cylinder 84 and consequently a slight outward radial displacement of the intermediate section 107 of the mold from the upper section 112 and from the lower section 106, avoiding in this way a harmful rubbing between the upper section 112 of the mold and the intermediate section 107.

When the vulcanizing unit is completely open, the plate 105 is raised to its maximum open position by injecting compressed fluid in the cylinders 95 and 96, which cause a further rotation of the lever 100 and the detachment of the block 101 from the stern 102 with a consequent axial upward displacement of the cylinder 84.

The raising of the plate 105 initiates the outward radial motion of the sectors 107 of the mold and therefore their mutual detachment.

The partially shaped tire 14-2 is then placed on the plate 91 in contact with the lower section 106 of the mold, truing up the lower bead of said tire on the corresponding profile of the edge of said plate 91, and the sprocket wheels 119 are actuated by means of the motor 135 in order to rotate the cover 114 to an angle slightly exceeding 90 and to a point where its edge is horizontal, and to lower it until the inner edge of the upper section 112 of the mold engages the upper bead of the tire 142. The motor 135 is then stopped and compressed fluid is injected through the opening 141, provided in the cylinder 140, in order to push the inner bag 144 downward housed into said cylinder and to insert it progressively inside the tire 142, starting from its clamped edge 143.

The curing bag 144, having a toroidal shape corresponding to the shape of the final inner profile of the tire 142, fits perfectly with the inner surface of the latter without any occurrence of folds. The motor 135 is now actuated in order to rotate the sprocket wheels 119 until the pivots 118 have reached the lower position, represented in FIG. 7, corresponding to the bottom dead center. As a result of this rotation the lower surface of the plate 113 moves downwardly and then contacts the upper surface of the supports 108 of the sectors 107, whereas the upper bead of the tire is brought to its definitive distance with respect to the other bead and the tire makes complete contact both with the lower section 106 of the mold and with the upper section 112. Then the plate 113, during its lowering, pushes the plate 105 downwardly together with the elements supported by it with a pressure higher than that exerted by the fluid under the pistons of the cylinders 95 and 96 which control the axial displacement of the cylinder 84, so that the fluid is caused to return in the feeding pipe. The lowering motion of the plate 105 causes the plates 109 to slide along the fixed plates 110, thus originating the radial approach of the sectors 107 which, by means of their projections, penetrate the surface of the tread of the pneumatic tire 142 and completely enclose the mold, the compressed fluid having been previously released from the cylinder 103. At this moment also the cover 114 comes in contact with the upper edge of the container 82, isolating the mold from the outer room, and the block 101 comes in contact with the stem 102. The tire is then vulcanized in the conventional Way by injecting additional compressed fluid into the curing bag 144 through the opening 141, so as to increase its inner pressure, and injecting compressed steam into the container 82 through the opening 83.

After vulcanization, the pressure inside the container 82 is reduced and the compressed fluid contained in the curing bag 144 is released in order to create such a difference of pressure on the opposite faces of the curing bag that the bag is caused to automatically reenter housing 140.

The vulcanizing unit is then opened again, as described above and the condensate formed in the cylinder 140 is automatically released through the opening 141, the cover 114 being rotated to an angle exceeding with respect to the horizontal plane. Finally, the vulcanized tire is removed from the lower section 106 of the mold by injecting compressed fluid through the opening 85 of the cylinder 84 and consequently by raising the piston 86 which pushes the plate 91 upwardly, supported by the stem 89.

In order to bring again the plate 91 in contact with the lower section 106 of the mold, before treating a new tire, the compressed fluid is released from the cylinder 84 through the opening 85 and compressed fluid is injected over the piston 86 through the opening 87, the tube 88 and the opening 90.

To replace the curing bag 144 with another one, the endless screw 136 is rotated in order to axially displace the cylinder 140 and to release the thickened edge 142 of the curing bag 144.

The method of this embodiment offers the following advantages with respect to the embodiment as shown by FIG. 5:

(a) Elimination of the mechanical means both for the introduction and, in particular, for the removal of the flexible diaphragm from the hollow article. In this way, besides obtaining a considerable simplification of the apparatus, it is possible to provide it with mechanical means to automatically detach and raise the treated article from the lower section of the mold.

(b) Elimination of all the above described inconveniences due to the formation of folds in the diaphragm during its introduction in the hollow article. In fact, the adoption of a diaphragm of toroidal shape, whose profile corresponds to the final inner profile of the article to be treated, facilitates the insertion of the diaphragm in said article and its uniform distribution inside the latter.

(c) Disposition of the diaphragm into a cylindrical housing situated in the upper part of the machine. Consequently the condensate formed on the face of the diaphragm opposite to that which comes in contact with the compressed fluid, is not collected in said diaphragm, but drops on the lower section of the mold, still hot for the heat treatment to which the preceding article has been subjected, and then evaporates, departing from the same.

(d) Adoption of an auxiliary means for determining small radial displacements of the sectors which constitute the intermediate section of the mold on its reopening, so that harmful rubbings between the surfaces in mutual contact of the upper section of the mold and of said sectors can be avoided. These rubbings, in fact, can originate considerable scorings, in particular in the most general case in which the material constituting said sectors has a hardness very different from that of the material constituting the two continuous annular sections of the mold.

The embodiment shown in FIGS. 9-11 is similar to that of FIGS. 5 and 6, but some details have been modified to make it particularly suitable for differentiated heat treatment of the article, on the peripheral band of which the desired embossed pattern has been printed.

The apparatus shown in FIGS. 9 and 10 comprises a circular plate 201, which supports a second plate 202 provided with a cavity 203. A duct 204 passes through the walls of the plates 201 and 202 and serves for the injection and the discharge of a heated fluid in the cavity 203. The plate 202 carries the lower section 205 and the central section 206 of a mold. The lower section 205 has a continuous annular shape, whereas the central section 206 is subdivided into a plurality of sectors provided on their inner surface with projections corresponding to the recesses to be produced in the band when molded.

The sectors 206 are assembled on supports 207, each of which is provided with lateral guides 208 and with an inclined plane 209, disposed between the guides 208. In contact with the inclined plane 209 and inserted between each pair of guides 208, there is a second inclined plane 210, integral with the frame 211 of the curing unit by means of the supporting ring 212, provided with an annular cavity 213. A duct 214 passes through the wall of the ring 212 and serves for the injection and the dis charge of heated compressed fluid inside the cavity 213.

The upper section 215 of the mold is supported by a plate 216, provided with a cavity 217. A duct 218 passes through the wall of the plate 216 and serves for the injection and the discharge of heated compressed fluid inside the cavity 217. The plate 216 is integral with a plate 219 assembled inside the lid 220 of insulating container 221. In the central part of the plates 216 and 219 there is slidably assembled .a stem 222, having a lower end portion of hemispherical shape. The stem 222 is actuated by a piston, not shown.

In the central part of the circular plates 201 and 202 there is assembled a cylinder 223 extending downwardly, which is provided at its lower end with an opening for the introduction of curing fluid. Between the lower section 205 of the mold and the cylinder 223 there is clamped the thickened edge 224 of a flexible curing bag 225. The plate 201 and the elements supported by it may be elevated by a piston not shown.

In order to mold the tread band of a tire 226, which is at least partially shaped, and to cure said tire, the plate 201 is initially raised to bring it to the position shown in FIG. 9 in order that the sectors 206 may be detached from the lower section 205 of the mold. Then the tire 226 is disposed on the lower section 205 of the mold and the plate 219 and the lid 220 are lowered until the section 215 of the mold reaches the upper bead of the tire 226. Then the stem 222 is pushed downwardly and compressed fluid is injected through the opening provided on the bottom of the cylinder 223. Accordingly, the compressed fluid pushes upwardly the curing bag 225, contained in the cylinder 223, and causes the central part of said curing bag to engage with the lower end of the stem 222. This is then progressively withdrawn towards the top, so that the curing bag 225 may gradually mate with the inner surface of the tire 226, starting from its clamped edge. At this stage the upper section 215 of the mold is lowered again. When the lower surface of the plate 216 comes into contact with the upper surface of the sectors 206 and of their supports 207, the tire beads are at their mutual final distance and the tire is in contact with the inner surface of the sections 205 and 215 of the mold. The plate 216, in its further downward movement, pushes the plate 201 and the elements supported by it downwardly under a pressure higher than that exerted by the fluid existing below the piston, which had raised the plate 201, so that said fluid is compelled to return to its feeding pipe. The lowering of the plate 201 causes the sliding of the inclined planes 209 along the stationary inclined planes 210, thus causing the radial approaching of the sectors 206, the projections of which completely penetrate the tread band, and the complete closure of the mold. At this moment also the lid 220 comes into contact with the upper edge of the container 221, isolating the mold from the outer room. Then the curing of the tire is carried out, by injecting additional compressed fluid in the curing bag 225 in order to increase the pressure in its inside and by injecting compressed steam in a continuous way in the cavities 203, 213 and 217, through the ducts 204, 214 and 218, respectively. Steam at different temperatures, pre-established in accordance with the thickness of the single parts of the tire and with the type of compound constituting them, may be injected in the cavities 203, 213 and 217. After curing, the tire 226 is removed from the mold by repeating the above described operations in an inverted sequence, and the curing bag 225 is removed from the inside of the tire 226 by pushing it inside the cylinder 223 by means of the stem 222 The embodiment shown in FIG. 11 is similar to that illustrated in FIGS. 9 and 10, but substantially ditfers from that of FIG. 9 as regards the curing bag 262. This curing bag has a tubular shape, and one of its thickened edges 264 is clamped between a ring 266 and a plate 268 integral with the lower section 238 of the mold. The other thickened edge 270 of the curing bag 262 is also clamped between a ring 272 and a circular plate 274 integral with the upper end of a stem 276 slidably assembled inside a hollow stern 278, the upper end of which is integral with the plate 230. The stems 276 and 278 are actuated by two pistons not shown.

Plate 230 supports a second plate 232 provided with a cavity 234. A duct 236 passes through the walls of plates 230 and 232 and serves for the injection and discharge of a heated fluid in cavity 234.

The sectors 240 are assembled on supports 242, each of which is provided by lateral guides 244 and with an inclined plane 246 disposed between the guides 244. In contact with the inclined plane 246, and also extending between guides 244, is a second inclined plane 248, integral with frame 250 by means of the supporting ring 252 provided with an annular cavity 254. A duct 256 passes through the wall of the ring 252 and serves for the injection and discharge of heated compressed fluid inside cavity 254.

FIG. 11 illustrates moreover a cylindrical container 280 which is in the indicated position only during the insertion of the curing bag in the tire 260.

To mold the tread band of the tire 260, which is at least partially shaped, the plate 230 is brought to the preestablished upper position shown in FIG. 11 in order that the central sectors 240 of the mold may be spaced from the lower section 238, and the plate 274 is elevated until the curing bag 262 assumes a cylindrical shape. The tire 260 is telescopically inserted about the bag 262 and its lower bead is caused to engage with the lower section 238 of the mold. Then the cylindrical container 280 is also telescopically inserted about the bag 262 and is lowered until its lower edge engages with the upper bead of the tire 260. The plate 274 is progressively lowered and at the same time, through an opening not shown, compressed fluid is injected inside the bag 262 which, sliding along the inner surface of the container 280, gradually penetrates inside the tire 260 and mates with its inner surface. When the curing bag 262 is completely penetrated inside the tire 260, the container 280 is removed and the lid of the curing unit, not shown, is lowered.

While the lid of the curing unit lowers, the upper half mold, which is fast with it, engages on the upper bead of the tire and pushes it downwardly until it has reached the final distance from the other bead. At this stage additional compressed fluid is injected inside the curing bag 262 to oppose the pressure which is exerted immediately afterwards on the tread band by the sectors 240 due to the sliding of the inclined planes 246 along the inclined planes 248 because of the lowering of the plate 230, pushed downwardly by the upper part of the curing unit. When the mold is completely closed, additional compressed fluid is injected inside the curing bag 262 to increase the pressure inside it and the curing operation is carried out by injecting heating fluids in cavities 134 and 254.

For the removal of the cured tire from the mold, the above indicated operations are repeated in an inverted sequence. In this second phase, however, the presence of the container 280 is not necessary.

It is understood that the constructional details of the devices which control the radial displacement of the central sectors of the mold and of those which control the introduction or the removal of the tire curing bag may be varied without prejudicing the spirit and scope of the present invention.

Likewise, also when the article to be molded is hollow and impermeable, the presence of an inflatable core is not necessary, since the fluid may be injected in direct contact with the inner surface of the article.

The embodiment of FIGS. 9-11 offers the advantage that it is possible to graduate at will the intensity of the heat treatment of the various parts of the article, on the tread band of which the pattern has been previously printed.

Since the entire article is to be subjected to a heat treatment lasting for an equal period of time, in order to vary the intensity of the heat treatment, resort is to be had to a differentiation of the temperaures of the fluid injected into the cavities 234 and 254 provided in the proximity of the mold sections. For instance in a pneumatic tire, in which the composition of the compound constituting the tread band and the thickness of the latter are different from those of the sidewalls, it may be sometimes advantageous to inject a fluid at a higher temperature in the cavities nearest to the sectors which constitute the central section of the mold rather than in the cavities adjacent to the continuous sections of the mold.

What is claimed is:

1. A method of forming an embossed pattern upon the peripheral surface of an article of toroidal cross section comprising the steps of first confining all the exterior surfaces of said article except the peripheral surface thereof between rigid surfaces, and subsequently simultaneously bringing a plurality of additional surfaces having projections corresponding to theembossed pattern into contact with said peripheral surface along the entire extent thereof, in order to confine said article completely and to produce cavities in the peripheral surface thereof in accordance with the embossed pattern.

2. A method of forming an embossed pattern upon the peripheral surface of an article of toroidal cross section comprising the steps of first confining all the exterior surfaces of said article except the peripheral surface thereof between rigid surfaces, exerting a pressure greater than atmospheric pressure uniformly upon the entire inner surface of said article, and subsequently simultaneously bringing a plurality of additional surfaces having projections corresponding to the embossed pattern into contact with said peripheral surface along the entire extent thereof at a pressure lower than the pressure exerted upon the inner surface of the article, in order to confine said article completely and to produce cavities in the peripheral surface thereof in accordance with the embossed pattern.

3. A method of forming an embossed pattern upon the peripheral surface of an impermeable article of toroidal cross section comprising the steps of first confining all the exterior surfaces of said article except the peripheral surface thereof between rigid surfaces, injecting compressed fluid into said article, and subsequently simultaneously bringing a plurality of additional surfaces having projections corresponding to the embossed pattern into contact with said peripheral surface along the entire extent thereof at a pressure lower than the pressure exerted upon the inner surface of the article, by said fluid, in order to confine said article completely and to produce cavities in the peripheral surface thereof in accordance with the embossed pattern.

4. A method of forming an embossed pattern upon the peripheral surface of an article of toroidal cross section comprising the steps of introducing a curing bag into the article, confining all the exterior surfaces of said article except the peripheral surface thereof between rigid surfaces injecting compressed fluid into said bag, and subsequently simultaneously bringing a plurality of additional surfaces having projections corresponding to the embossed pattern into contact with said peripheral surface along the entire extent thereof at a pressure lower than that exerted on the inner surface of the article by means of said bag, in order to confine said article completely and to produce cavities in the peripheral surface thereof in accordance with the embossed pattern.

5. A method of forming an embossed pattern upon the tread band of a pneumatic tire while said band is in a plastic state comprising the steps of engaging the adjacent bead of said tire with a first continuous mold section, engaging the other bead with a second continuous mold section, moving said beads towards each other to a pre determined spaced apart position, introducing a flexible curing bag inside said tire while simultaneously confining all the exterior surfaces of said tire except the tread band within said mold sections, injecting compressed fluid into said bag, and subsequently simultaneously bringing a plurality of additional mold sections having projections corresponding to the embossed pattern into contact with said tread band along the entire extent thereof at a pressure lower than that exerted on the inner surface of the band by means of said bag, in order to confine said tire completely and to produce cavities in the tread band in accordance with the embossed pattern.

6. The method of claim 3, wherein the bag is introduced into said tire by the steps of anchoring one edge of said bag on one of said continuous mold sections, and directing the bag towards the other of said continuous mold sections while simultaneously delaying displacement of the central portion of said bag in order to insure perfect truing up thereof.

7. The method defined by claim 3, including the step of surrounding the toroidal article with heated fluid after the article has been completely enclosed within the rigid surfaces.

8. The method defined by claim 3, including the step of supplying heated fluid at varying temperatures through a plurality of cavities formed adjacent said rigid surfaces.

9. A method of printing an embossed pattern upon the tread band of a pneumatic tire while said band is in a plastic state, comprising the steps of telescopically threading the tire about a flexible curing bag and causing a bead of the tire to engage a continuous section of a mold, threading a rigid tubular body about the curing bag and causing an edge portion of said tubular body to engage the other bead of the tire, moving the edge portion of the curing bag contained in said tubular body towards said other bead by sliding the bag along the inner surface of said tubular body and simultaneously injecting compressed fluid in said curing bag to cause the bag to adhere to the inner surface of the tire, moving the tire heads towards each other to predetermined spaced apart positions, enclosing the tire within said continuous section and another continuous sections of said mold without engaging said tread band, and subsequently bringing at least one additional mold section having projections corresponding to the embossed pattern into contact with said tread band at a pressure lower than that exerted on the inner surface of the tread band by means of said bag, in order to enclose said tire completely and to produce cavities in the tread band in accordance with the embossed pattern.

10. The method defined by claim 9, including the step of surrounding the tire with heated compressed fluid, after the tire has been completely enclosed within the sectional mold.

11. The method defined by claim 9, including the step of supplying heated fluid at varying temperatures through a plurality of cavities formed adjacent said mold.

12. A method of heat treating and forming an embossed pattern upon the peripheral surface of an article of toroidal cross section comprising the steps of first confining all the exterior surfaces of said article except the peripheral surface thereof between rigid surfaces, progressively inserting a flexible curing bag into the article by inserting compressed fluid into the bag, and subsequently simultaneously bringing a plurality of additional surfaces having projections corresponding to the embossed pattern into contact with said peripheral surface along the entire extent thereof at a pressure lower than that exerted on the inner surface of the article by means of said bag in order to form a mold confining said article completely and to produce cavities in the peripheral surface thereof in accordance with the embossed pattern.

13. The method of claim 12, further comprising the steps of creating a positive difference of pressure between the outer surface and the inner surface of said bag in order to cause its expulsion from the inside of the article, and opening the mold to remove the treated article.

14. The method of claim 12, further comprising the steps of enclosing said mold within a fluid tight container, injecting heated compressed fluid into said container at a pressure lower than that inside the flexible curing bag, discharging the compressed fluid from the flexible curing bag and simultaneously reducing the pressure inside the container in order to create a positive difference of pressure between the outer surface and the inner surface of the flexible curing bag sufiicient to cause the expulsion of the flexible curing bag from the inside of the hollow article, completely discharging the compressed fluid from the container, and opening the mold to remove the treated article.

15. A method of forming an embossed pattern upon the tread band of a pneumatic tire while said band is in a plastic state, comprising the steps of engaging the adjacent head of said tire with a first continuous mold section, engaging the other head with a second continuous mold section, moving said heads towards each other to a predetermined spaced apart position, enclosing all the exterior surfaces of said tire except the tread band within said mold sections, while simultaneously inserting a flexible curing bag inside said tire and filling the bag with a compressed fluid, subsequently bringing at least one additional mold section having projections corresponding to the embossed pattern into contact with said tread band at a pressure lower than that exerted on the inner surface of the band by means of said bag, in order to enclose said tire completely and to produce cavities in the tread band in accordance with the embossed pattern, subsequently creating a difference of pressure between the outer surface and the inner surface of the flexible bag in order to cause its expulsion from the inside of the tire, and opening the mold to remove the treated tire.

16. A method of forming an embossed pattern upon the tread band of a pneumatic tire while said band is in a plastic state, and vulcanizing said tire, comprising the steps of engaging the adjacent bead of said tire with a first continuous mold section, engaging the other bead with a second continuous mold section, moving said heads towards each other to a predetermined spaced apart position, enclosing all the exterior surfaces of said tire except the tread band within said mold sections, while simultaneously inserting a flexible curing bag inside said tire and filling the bag with compressed fluid, subsequently bringing at least one additional mold section having projections corresponding to the embossed pattern into contact with said tread band at a pressure lower than that exerted on the inner surface of the band by means of said bag, in order to enclose said tire completely and to produce cavities in the tread band in accordance with the embossed pattern, enclosing the mold into a fluid tight container, injecting heated compressed fluid into said container at a pressure lower than that inside the curing bag, discharging the compressed fluid from the flexible curing bag and simultaneously reducing the pressure inside said container in order to create a positive difference of pressure between the outer surface and the inner surface of the curing bag suflicient to cause the expulsion of the flexible curing bag from the inside of the tire, completely discharging the compressed fluid from the container, and opening the mold to remove the treated tire.

17. A method as in claim 16, wherein the flexible bag has a toroidal shape corresponding to the final inner profile of the hollow article to be obtained.

18. A method as in claim 17, wherein said additional mold section is formed by a plurality of sectors and wherein the opening of the mold after the treatment of the article contained therein comprises the steps of moving one of said continuous mold sections away from the other continuous mold section, removing the sectors from the peripheral surface of the treated tire, and then mechanically removing the tire from said other continuous mold section.

19. A method as in claim 18, wherein simultaneously with the initial moving of said one of said continuous mold sections away from the other, there is carried out a first slight mutual radial detachment of the sectors and then a second radial detachment of said sectors after the moving of said one of said continuous mold sections away from the other has been completed.

References Cited UNITED STATES PATENTS 1,159,792 11/1915 Paynter.

1,354,227 9/1920 Thompson.

2,023,002 12/1935 Bosomworth.

2,880,458 4/1959 Frohlich et al. 264-315 2,997,738 8/1961 Soderquist 264-315 ROBERT F. WHITE, Primary Examiner N. RUSHEFSKY, Assistant Examiner US. Cl. X.R. 

